This research program consists essentially of 1) continuing our investigation of the etiology and mechanism of cataractogenesis in animal model systems, and 2) applying our positive findings to the study of human cataracts. Studies on biochemical and biophysical characteristics of lens proteins and their changes in the process of lens opacification have been progressing as proposed. Fractionation of the normal and galactose-induced cataractous rat lenses revealed six distinctive fractions (I-VI) by gel chromatography in this laboratory. Fraction II (F-II) is a group protein that exists in the normal rat lens soluble protein but vanishes in the 5 plus (severe) cataractous lens. This group of proteins has been characterized by this research group and work is in progress toward the determination of the primary structure. The role of F-II in cataractogenesis is of interest and significancy. The sequential changes of protein in neonatal rat lens have yielded information on the biosynthetic pattern of rat lens protein. The distribution of molecular weights species of the soluble protein in normal and galactose-induced cataractous rat lens has been completed. It is planned to characterize as well as to determine the distribution and molecular weights of the soluble protein in normal and cataractous human lenses. An important question to be answered is why the soluble protein pattern changes observed in cataractous human lens have been found to be different from those in the rat lens during cataractogenesis.